This application claims benefit of priority to Japanese Patent Application No. JP10-252681 filed Sep. 7, 1998, the entire disclosure of which is incorporated by reference herein.
1. Field of the Invention
The present invention relate, to an elevator provided with an emergency stop device.
2. Description of the Background
A conventional elevator apparatus is composed of an elevator shaft extending vertically in a building, and a machine room (penthouse) located right over the shaft and having a motor and the like. This elevator apparatus further includes a sheave located in the machine room and driven by the motor, a cage disposed in the shaft and connected to one portion of a cable that is wound on the sheave, and a counterweight connected to another portion of the cable and balanced with the cage. The cage is moved up and down by rotating the sheave in the machine room. The cage and the counterweight are guided by means of guide rails arranged in the elevator shaft.
With the increased construction of high-rise buildings, the operating speed of elevators is becoming higher and higher, thus requiring a satisfactory safe measure. To cope with this, the conventional elevator apparatus is provided with an emergency stop device that can stop the cage safely and securely in case the cage for any reason suddenly descends at a speed higher than its rated speed. One example of the emergency stop device is disclosed in U.S. Pat. No. 5,377,786.
The emergency stop device is composed of a governor, a cable passed through the governor and adapted to be restricted in motion when the cage descends at a speed higher than its rated speed, and a stop mechanism attached to the cage and capable of braking and stopping the cage. The stop device further has a link mechanism, which connects the cable and the stop mechanism and actuates the stop mechanism through the medium of the relative movements of the cable and the cage when the cable is restricted in motion.
The emergency stop mechanism, which is located at the lower end portion of the cage, includes a holding member having a V-shaped slit gradually spreading downward and a stopper member slidable in the slit. The emergency stop device brakes the cage in a manner such that the stopper member moves up to cause each guide rail to be held tight in the slit of the holding member by an wedge effect.
The link mechanism includes a driving lever, which is attached to the upper part of the cage and fixed to the cable extending from the governor, and a lift rod connecting the driving lever and the slit member of the stop mechanism. The lift rod extends along the height direction of the cage, and serves to pull up the slit member of the stop mechanism at the lower end of the cage thereby actuating the stop mechanism.
Further, the link mechanism is provided with a limit switch, which detects the actuation of the link mechanism and outputs a hoisting machine stop command signal. Once the limit switch detects a shift of the driving lever and delivers the stop command signal to a control device, it continues to output the command signal.
In canceling an emergency stop state and restarting the elevator apparatus, the guide rail is released from the hold in the slit by means of the stopper member by, for example, pulling up the cage, whereby the restraint on the ascent and descent of the cage by the emergency stop device is removed. An operator gets on the cage and manually resets the limit switch to its initial state, thereby enabling the elevator apparatus to be restarted.
In the conventional elevator apparatus described above, the link mechanism is attached to the upper end portion of the cage, so that a relatively long member is used as the lift rod for connecting the stopper member of each emergency stop device and the driving lever. It is difficult, therefore, to keep the lift-mechanism in an assembled state when it is shipped from the factory. Thus, the lift mechanism must be assembled during installation of the elevator in the building.
Since the elevator shaft is relatively narrow, assembling the link mechanism in the building requires much time and labor. Since the lift rod is a relatively long member, moreover, each link mechanism must be finely adjusted as it is assembled, in order to assure normal operation. Thus, the installation work entails high costs.
If the link mechanism is attached to the lower end portion of the cage with the lift rod shortened so that the mechanism can be in the assembled state as it is shipped from the factory, furthermore, the limit switch must be also attached to the lower end portion of the cage.
If the limit switch is attached to the lower end portion of the cage, it is difficult for the operator to reset the limit switch manually to the initial state in restarting the elevator apparatus after once actuating the emergency stop device. Thus, the elevator apparatus cannot be restarted with ease.
Accordingly, one object of the present invention is to provide an elevator characterized by reduced installation costs and the like.
Another object of this invention is to provide an elevator apparatus capable of being easily restarted after an emergency stop device is once actuated to restrain a cage from ascending or descending.
These and other objects are achieved according to the present invention by providing a novel elevator including a cage configured to ascend and descend along a guide rail in an elevator shaft, a drive unit for moving the cage up and down, and an emergency stop device configured to urgently stop the cage when the cage descends at an extraordinary speed and including an emergency stop mechanism provided at a lower end portion of the cage and configured to engage the guide rail, thereby urgently stopping the cage, a link mechanism provided at the lower end portion of the cage so as to be located close to the emergency stop mechanism and configured to actuate the emergency stop mechanism on receiving an external input, and a speed detector configured to detect the descent of the cage at the extraordinary speed and correspondingly to apply the external input to the link mechanism.